Habitat loss (and consequent fragmentation) is one of the biggest drivers of biodiversity loss (1). As anthropogenic land use change has increased, there is a lower amount of available habitat and greater isolation between remaining habitat patches. This reduces the ability of species to move between habitat patches across the landscape, also known as functional connectivity (2). Maintaining functional connectivity is key to conserving metapopulations and reducing species' exctinction risk, especially as the climate warms (3).

Measuring connectivity is crucial for informing conservation planning and developing effective policies. Previous efforts to quantify connectivity are time and labour intensive, relying upon mark-release-recapture (4) or using genetic sampling (5), which are often only applicable at small spatial scales.

Larger scale (national) indicators have tended to focus on structural metrics based on land cover combined with expert opinion on species' habitat associations and movement capacity (6). While useful, these approaches are limited by the frequency by which land cover data are updated and are rarely validated using empirical data.

An alternative method to measuring connectivity has been proposed based on a measure of population synchrony - the level of correlation in time series of annual population growth rates between different locations. Population synchrony is known to be driven by shared climate, distance between sites, and habitat similarity (7,8). After accounting for these factors, more synchronised populations tend to be more connected by movement (9). Population synchrony can therefore be used to obtain a signal of functional connectivity which tells us whether our landscapes are becoming more or less fragmented.

This new method, which uses data from the UK Butterfly Monitoring Scheme, the Common Bird Census, and the Breeding Bird Survey, demonstrates how we can use widely available, annually updated monitoring results to provide a data-driven, 'species-eye-view' of functional connectivity.

The national indicator of connectivity demonstrates that apparent declines in connectivity for butterflies seen from 1985 and 2000 are being reserved and butterflies are becoming more connected. This could be in response to the uptake of agri-environment schemes which promote wildlife friendly management and have been shown to increase butterfly numbers (10). Woodland birds on the other hand show no strong changes overall, but a few species are increasing in connectivity, possibly driven by increased woodland planting in recent years (11).

Our findings highlight how long-term monitoring data could be used to inform conservation management and the underlying methodology to this indicator are currently used as an experimental statistic of habitat connectivity in the Defra/JNCC Biodiversity Indicators. As part of the 25-year Environment Plan, the UK Government aims to create a Nature Recovery Network in order to reduce biodiversity loss, improve resilience to climate change, and enhance well-being. Assessing changes in connectivity over time, using indicators such as the one developed here, will become crucial to determine whether we are going to meet the target of creating more, bigger, better, and connected areas of habitat. 

Lisbeth Hordley, Ecological Statistician, Butterfly Conservation


1. Butchart, S.H.M., Walpole, M., Collen, B., van Strien, A., Scharlemann, J.P.W., Almond, R.E.A., Baillie, J.E.M., Bomhard, B., Brown, C., Bruno, J., Carpenter, K.E., Carr, G.M., Chanson, J., Chenery, A.M., Csirke, J., Davidson, N.C., Dentener, F., Foster, M., Galli, A., Galloway, J.N., Genovesi, P., Gregory, R.D., Hockings, M., Kapos, V., Lamarque, J.F., Leverington, F., Loh, J., McGeoch, M.A., McRae, L., Minasyan, A., Morcillo, M.H., Oldfield, T.E.E., Pauly, D., Quader, S., Revenga, C., Sauer, J.R., Skolnik, B., Spear, D., Stanwell-Smith, D., Stuart, S.N., Symes, A., Tierney, M., Tyrrell, T.D., Vié, J.C., Watson, R. (2010) Global biodiversity: Indicators of recent declines. Science 328 (5982): 1164-1168. doi:10.1126/science.1187512

2. Hanski, I. (1998) Metapopulation dynamics. Nature 396 (6706): 41-49. doi.org/10.1038/23876 

3. Hanski, I. & Gilpin, M. (1991) Metapopulation dynamics: brief history and conceptual domain. Biological Journal of the Linnean Society 42: 3-16. doi:10.1111/j.1095-8312.1991.tb00548.x

4. Roland, J., Keyghobadi, N., Fownes, S. (2000) Alpine Parnassius Butterfly Dispersal: Effects of Landscape and Population Size. Ecological Society of America 81: 1642-1653. doi.org/10.1890/0012-9658(2000)081[1642:APBDEO]2.0.CO;2

5. Fenderson, L.E., Kovach, A.I., Llamas, B. (2020) Spatiotemporal landscape genetics: Investigating ecology and evolution through space and time. Molecular Ecology 29 (2): 218-246. doi:10.1111/mec.15315

6. Watts, K. & Handley, P. (2010) Developing a functional connectivity indicator to detect change in fragmented landscapes. Ecological Indicators 10: 552-557. doi:10.1016/j.ecolind.2009.07.009

7. Powney, G.D., Roy, D.B., Chapman, D., Brereton, T., Oliver, T.H. (2011) Measuring functional connectivity using long-term monitoring data. Methods in Ecology and Evolution 2: 527-533. doi:10.1111/j.2041-210X.2011.00098.x

8. Powney, G.D., Broaders, L.K., Oliver, T.H. (2012) Towards a measure of functional connectivity: Local synchrony matches small scale movements in a woodland edge butterfly. Landscape Ecology 27: 1109-1120. doi:10.1007/s10980-012-9771-y

9. Oliver, T.H., Powney, G.D., Baguette, M., Schtickzelle, N. (2017) Synchrony in population counts predicts butterfly movement frequencies. Ecological Entomology 42 (3): 375-378. doi:10.1111/een.12391

10. Hardman, C.J., Harrison, D.P.G., Shaw, P.J., Nevard, T.D., Hughes, B., Potts, S.G., Norris, K., Marini, L. (2016) Supporting local diversity of habitats and species on farmland: A comparison of three wildlife-friendly schemes. Journal of Applied Ecology 53 (1): 171-180. doi:10.1111/1365-2664.12557

11. Forestry Commission (2018) Forestry Statistics 2018: A compendium of statistics about woodland, forestry and primary wood processing in the United Kingdom. https://www.forestresearch.gov.uk/tools-and-resources/statistics/forestry-statistics/forestry-statistics-2018/